I was going through some of my old rocketry info piles the other day and came across a catalog from Competition Model Rockets, circa 1970 or so. One of the rockets in the catalog was the Break Away, a parachute duration model with a rather interesting split airframe, side deployment parachute recovery feature. I was thrilled to find the plans here, but I am wondering if anyone has had any recent experience either building or cloning it, and whether the side deployment feature worked well with the 28" 'chute?

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John

Was CAR-ACF# S 337
Was NAR# 91049
Was SAM# 0323

Life begins when the countdown reaches zero!

I built one a few years ago using parts from Pratt Hobbies. The fit between the two halves was finicky as I remember. You definitely had a larger hole to cram a bigger chute into a smaller diameter body. I've seen a trend though as FAI style techniques filter into NAR competition to make lighter larger diameter bodies to put in larger (30-36" and up) diameter chutes.

It's a philosophical difference between putting a small model higher with a smaller chute and putting a larger model lower but with a larger chute.

The break away was a way of thinking about a min diameter model differently, but it is a lot more complex than other approaches that don't start with a min diameter model.

kj

I agree with Kevin. In competition, the KISS principle definitely applies - the more complex the design, the more that can go wrong. The Break Away is neat, but more complex that necessary. I have routinely seen a larger diameter (30 or 40mm) parachute duration (PD) win regional contests over smaller diameter models. True, the smaller diameter model goes higher, but once you put decent thermal activity into play, the initial altitude of the rocket is meaningless. I would rather have a 30 inch chute catch even a weak thermal than a smaller (18 to 24 inch) chute catch the same thermal. The bigger chute will win. And if you couple the larger diameter model with fin root shock cord mounts, you even take snags and zippers out of the equation. A 40mm diameter model with a long kevlar shock cord mounted in the fin root will usually outperform a BT-50 model in all but the deadest of air. If you make that 40mm model really light (I build mine from 110# card stock and vellum - no need for glass and high tech in all but the fiercest of competition), the only real concern becomes: "will I get it back?". But for that second return flight, there's always the trusty old Alpha with a 12 or 15 inch chute!

So, as a novelty flight, the Break Away might be a lot of fun, but I could probably build two 40mm card and paper models in the same time it takes to build the one Break Away, and the 40mm models will most likely out perform the Break Away nine out of ten times.

Greg

Thanks for the feedback. I'm so intrigued by the Break-Away's design that I probably will build one just for the experience, and then put it up against a wider airframe, larger 'chute design in a head to head simultaneous launch comparison. I'm not sure what kind of thermal activity I'll get locally (especially at this time of year), so I may try the experiment at a few locations next summer.

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John

Was CAR-ACF# S 337
Was NAR# 91049
Was SAM# 0323

Life begins when the countdown reaches zero!

The instructions got me interested so I started a BT-55 version the other night. It will fly on 18mm motors and I plan on jamming the largest parachute I possibly can into it and see what happens. I went with the larger scale since I have not done any tube cutting like this before and I figured the larger size would give me something more to work with. One concern I have right now is whether the tubes will hold their shape in the center of the separation. In hindsight I should have used the heavy wall ST-125 I have in the box... Oh well, we'll see what happens.

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Kurt Knox
NAR #93503
MASA section 576
SAM #0316

Longitudinal cuts on a tube are relatively easier with a piece of aluminum right angle and make several light passes along the straightedge. Try the 3/8 x 1/2. Could you use brass strip ribs to hold the semi-circular shape?

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Gravity is a harsh mistress
SAM 002
NAR 91005
"The complexity of living is eminently favored to the simplicity of not."

I would think a semi-circular balsa disk about where the front wire hook is would help keep the shape of the front fairly well with limited weight/space penalty.

kj

Having known Col. Kuhn and having built several of his CMR kits, my one brief attempt at a Breakaway model decades ago did not go well.
Having served as Launch Officer for seveal Internats Team fly-offs at NARAM, I have learned a great respect for the larger diameter models that kevinj mentioned early in this thread.
But, what I keep going back to is that since the early competition models the best design change was the external shock cord anchored to a fin and taped to allow the booster to hang horizontally. This moved the shock cord anchor from internal to external, allowing for a body tube without anything a recovery device could hang up on.
In my humble opinion, better than cutting body tubes lengthwise.

My 1/50 of a dollar.

__________________
Charles Russell, MSgt,USAF (ret.)
NAR 9790, Lvl 1
SAM "Balls Three"

Grain across the longest opening.

__________________
Gravity is a harsh mistress
SAM 002
NAR 91005
"The complexity of living is eminently favored to the simplicity of not."

Tube is cut and coupler is shaped, also CA'ed the edges for durability. Waiting on a white box of goodness for needed parts to finish this "experiment".

__________________
Kurt Knox
NAR #93503
MASA section 576
SAM #0316